How to create a lossy JPEG 2000 picture?

Question

Hi there.
Now I am working on an app. to compare the quality between a traditional JPEG and the new JPEG2000 format.
Although I did not find the ways to encord JPEG2000 format in basic JAI, another API jai_imageio-1_0_01 does provide the way to do it.
The default parameter in the J2KImageWriteParam is for a lossless encord, the result is perfect, of course. But more importantly, I want to try the lossy ones so that I can reduce the outstream size.
The problem is here, when I just change the encoderate throught the setEncordingRate method, the result is terrible, which I am sure is a failure. I do not know why. There are many parameters I can set, does it mean I should change several at the same time, not just the encodingrate? And if I change the writeparam should I change the readparam too to decord?
My sample code is following, in it, I cpatured the screen as the source and write it into .jp2, then read it out to show.
Please help me, thanks a lot.
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import java.io.*;
import javax.media.jai.JAI;
import com.sun.media.imageio.plugins.jpeg2000.*;
import javax.imageio.stream.*;
import javax.imageio.ImageIO;
import com.sun.media.imageio.plugins.jpeg2000.J2KImageWriteParam;
import javax.imageio.*;
import javax.media.jai.operator.AWTImageDescriptor;
import javax.media.jai.RenderedOp;
class screen18 extends Frame{
     BufferedImage sh=null;//for Captured screen
     Rectangle screenSize;
     BufferedImage bi= new BufferedImage(1024, 768, BufferedImage.TYPE_INT_ARGB);           
     public screen18()
          addWindowListener(new WindowAdapter(){
          public void windowClosing(WindowEvent e){
          System.exit(0);
          screenSize = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
          sh= new BufferedImage(1024, 768, BufferedImage.TYPE_INT_ARGB);      
          //Capture the screen
          try{
               sh = (new Robot()).createScreenCapture(screenSize);
          }catch(Exception ex) {System.out.println(ex);}
     ImageWriter writer = (ImageWriter)ImageIO.getImageWritersByFormatName("jpeg 2000").next();
     ImageOutputStream ios = null;
     try {
          OutputStream os1 = new FileOutputStream("j2000.jp2");
          ios = ImageIO.createImageOutputStream(os1);
          writer.setOutput(ios);
          J2KImageWriteParam paramJ2K = new J2KImageWriteParam();
          //You can set whether it is lossy here
          //paramJ2K.setLossless(false);
          //paramJ2K.setFilter("w9x7");
          //paramJ2K.setEncodingRate(Double.MAX_VALUE*0.9);//key point
          System.out.println("JPEG2000 Parameter: ");
          System.out.println("getCodeBlockSize: "+paramJ2K.getCodeBlockSize());
          System.out.println("getComponentTransformation: "+paramJ2K.getComponentTransformation());
          System.out.println("getEPH: "+paramJ2K.getEPH());                               
          System.out.println("getLossless: "+paramJ2K.getLossless());
          System.out.println("getEncodingRate: "+paramJ2K.getEncodingRate());
          System.out.println("getFilter: "+paramJ2K.getFilter());           
          System.out.println("getProgressionType: "+paramJ2K.getProgressionType());           
          System.out.println("getSOP: "+paramJ2K.getSOP());
          System.out.println("getWriteCodeStreamOnly: "+paramJ2K.getWriteCodeStreamOnly());                     
          RenderedOp renImage7=AWTImageDescriptor.create(sh,null);
          IIOImage ioimage = new IIOImage(renImage7, null, null);
          writer.write(null, ioimage, paramJ2K);
          ios.flush();
          writer.dispose();     
     }catch (IOException ex) {System.out.println("Mistake is here when produce a J2K");}
          ImageReader reader1 = (ImageReader)ImageIO.getImageReadersByFormatName("jpeg 2000").next();
     try {                                              
          ImageInputStream iis = ImageIO.createImageInputStream(new File("j2000.jp2"));
          reader1.setInput(iis,false,true);
          J2KImageReadParam paramJ2K1 = new J2KImageReadParam();
          System.out.println(paramJ2K1.getDecodingRate());
          paramJ2K1.setDecodingRate(Double.MAX_VALUE*0.9);
               bi = reader1.read(0, paramJ2K1);
          reader1.dispose();
     }catch (Exception ex) {System.out.println("Mistake is here when extract a J2K");}     
     public void paint(Graphics g)
          g.drawImage(bi,0,0,this);
     public static void main(String args[])
          screen18 s = new screen18();
          s.setSize(1024,768);
          s.show();
}

Answer 1

Hi Wayne,
if you take a JPEG image from your file system as a source instead of the Robot, the lossy encoding works:
sh = ImageIO.read((new File("C:\\Images\\Bild0.jpg")));instead of
sh = (new Robot()).createScreenCapture(screenSize);and later...
paramJ2K.setLossless(false);
paramJ2K.setFilter("w9x7");
paramJ2K.setEncodingRate(Double.MAX_VALUE * 0.5);//key pointBest regards
Dominic